In the case of those roller conveyor systems of the above-mentioned kind which are known through use, carrier slides which carry goods to be transported or other objects are conveyed on a roller conveyor. Roller conveyor systems are particularly widely used in the automotive industry, to convey vehicle bodies or parts of them between individual workstations. In the automotive industry, the carrier slides are generally known as skids.
The known roller conveyors have multiple rollers, which are accommodated in roller rails which are arranged parallel to each other. Rollers which are opposite each other in pairs are in general connected to each other by a shaft. On one of the two roller rails, or between the two roller rails, a drive, which drives multiple rollers via chains or belts, is usually provided. Flanges on the rollers ensure that the carrier slides remain guided in the lateral direction during conveying.
By using additional functional units such as transverse movement vehicles, rotary tables and swing tables, complex conveying systems can be built up, and with them the goods or objects to be transported can be, for instance, distributed to different workstations. To control such complex roller conveyor systems, until now central stored program controllers have been used. From sensors which are arranged along the roller conveyor, the controller receives information about whether or not there is a carrier slide over the relevant sensor. In this way, the paths of the carrier slides over the roller conveyor can be followed. Because the controller also controls the transfer events on the functional units, the paths of the carrier slides can still be followed after such transfer events.
Fixing simply constructed data media on cross members of the carrier slides is also known. The known data media have eight prongs which are arranged like a comb and can be removed individually. In this way, numbers can be binary coded. These simple data memories can be read using sensors which are arranged centrally between two roller rails, and which detect the presence or absence of individual prongs. The sensors are directly connected to the controller, so that it obtains, at relatively large spatial intervals, information not only about whether a carrier slide is present at a certain location, but also about which carrier slides are involved.
However, it has been shown that more demanding control tasks cannot be implemented with these known roller conveyor systems, or only at very high cost. For one thing, in the case of the known roller conveyor systems all control tasks are combined centrally in one controller. This makes control slow and liable to faults, and also requires a high programming cost. To be able to identify the carrier slides with good spatial resolution, very many sensors are necessary, and despite the small memory content of the data memories they are relatively expensive to acquire and fit.
The present invention is directed to addressing these and other matters.